The first treatise on the law of evidence was William Nelson’s The Law of Evidence (1720) which consisted of numbered propositions founded on statutes and an analysis of over fifty series of legal reports compiled and published before 1700. No attempt was made to extract the underlying principles or to propound a theory of evidence. The book, however, inspired Geoffrey Gilbert’s and Thomas Peake’s classic works published in 1754 and 1801 respectively.
For Gilbert the whole corpus of the law of evidence can be subsumed under the Best Evidence rule: “that a man must have the utmost evidence, the nature of the fact is capable of; for the design of the law is to come to rigid demonstration in matters of right, and there can be no demonstration of a fact without the Best Evidence that the nature of the thing is capable of .. .”n. Peake, Gilbert’s successor, observed that the “extension of commerce, and the various concerns of mankind … rendered very large additions necessary” and stated the seven rules of evidence adopted by the common law of England. First, he who asserts must prove; he who denies need not prove. Second, the character of either party, unless put in issue by the very proceeding itself, cannot be called into question. Third, the best evidence the nature of the case will offer must be produced. Fourth, the law requires the testimony of a witness to be given on oath so that he may be examined and cross-examined. Fifth, hearsay statements are admissible as exception to the general rule where the facts, by their very nature, are incapable of positive and direct proof such as reputation, pedigree, prescription, custom and dying declaration. Sixth, admissions of a party are admissible as evidence against him. Seventh, the confession of an accused, voluntarily made, is evidence against him at his trial. Gilbert’s other successors such as Greenleaf, Taylor and Best accepted the Best Evidence rule as fundamental but Thayer reduced it to a counsel of prudence.
Writing in 1875, James Fitzjames Stephen based his theory on the doctrine of relevancy. Stephen opined:
"Evidence may be given in any proceeding of any fact in issue, and of any fact relevant to any fact in issue unless it is hereinafter declared to be relevant, and of any fact hereinafter declared to be deemed relevant to the issue:
Provided that the judge may exclude evidence of facts, which, though relevant or deemed to be relevant to the issue, appear to him too remote to be material under all the circumstances”
This doctrine of legal relevancy was transmogrified by Thayer into legal admissibility in this instructive passage:
"Admissibility is determined, first, by relevancy, - an affair of logic and experience, and not at all of law; second but only indirectly, by the law of evidence which determines whether any given matter which is logically probative is excluded."
But that is not all. Thayer, like Best, expatiated on the nexus between the theories of evidence and legal philosophy. For Thayer, legal reasoning is “an element common to all rational systems of proof’ and is required for the ascertainment of facts, the promotion of justice, maintaining established rights and existing governmental order. The ascertainment of facts, alluded to, depends not only on mathematical proof but also on “the ordinary rules of human thought and human experience sought in the ordinary sources, and not in the law books”. Legal philosophy, that part of legal theory which is concerned with general and abstract questions about law, is a rich tool box for deconstructing and reconstructing the adversarial system of justice; and to this we now turn.